Transmissible spongiform encephalopathies (TSE) or prion diseases are a group of transmissible neurodegenerative diseases associated with the misfolding of the endogenous cellular prion protein (PrPC) into a pathogenic isoform, termed PrPres, which is partially resistant to proteases and induces neurotoxicity [64]. The gene discussed is PRNP; the disease is prion disease.